During data transmission of a communication system, a clock signal is generated within a receiver when a transmitter provides only data signals but not a clock signal for the receiver to perform synchronization. FIG. 1A shows an ideal situation where a data signal, being free of jitter, has a frequency of f MHz, and a clock signal generated within a receiver has a frequency of 2f MHz. When the receiver latches every falling edge of the clock signal, correct latch data is obtained as shown in FIG. 1A. However, when jitter occurs in the data signal, timing drift is caused, resulting in errors in the latched data at the receiver, as shown in FIG. 1B. Suppose appropriate calibration is not carried out on the timing of the clock signal with respect to the signal jitter at the receiver, timing drift will increase with time and eventually lead to errors in all subsequent latched data.